The purpose of this project is to investigate the mechanisms by which injured neurons regenerate their nerve fibers and to evaluate neuronal and extra-neuronal factors that may influence the establishment of functional connections. Presently neuronal transplantation studies are being performed to determine whether neurons in homografts survive or are rejected by the immune response and whether neurons if they survive (immunosuppression may be needed to insure survival) can regenerate their nerve fibers and innervate appropriate end-organs. The results to date show that neurons can survive in homografts of ganglia if the recipient animal (rat) is rendered immunologically tolerant. Furthermore these neurons seem capable of surviving permanently (18 months to date) in the tolerant host and they can regenerate nerve fibers into tongue tissue and still perform their trophic function of inducing taste buds.